Balance-wheel lock



April 1961 R. H. THRASHER, JR 2,977,751

BALANCE-WHEEL LOCK Filed Aug. 21, 1956 INVENTOR RALPH H. THRASHER Jv. 43 45 BY 2 I ATTORNEY United States Patent 2,977,751 BALANCE-WHEEL LOCK Ralph H. Thrasher, Jr., 5113 72nd Place, Hyattsville, Md.

Filed Aug. 21, 1956, Ser. No. 605,455 3 Claims. (Cl. 58-107) (Granted under Title 35, U.S. Code (1952), sec. 266) The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the-payment of any royalties thereon or therefor.

This invention relates to a balance-wheel brake for a clock or the like, and more particularly to a balancewheel brake for a clock of the Hamilton chronometer type.

Before transporting a chronometer from one place to another, it is necessary to stop the clockwork in order to prevent injury thereto while in transit. This stoppage is commonly brought about by locking the balance-wheel against rotation, which prevents accidental damage to the balance-wheel and/or its supporting bearings. One common method of stopping, or locking, a balance wheel consists of wedging small cork wedges between the lower edge of the balance-wheel rim and adjacent,

stationary, mechanism supporting structure of the chro nometer.

In order to lock the balance-wheel of a chronometer, as for example by the method described above, it is necessary to remove the chronometer from its case. Removal of a chronometer from its case has the disadvantage of allowing dust and/or moisture to enter and damage the clockwork, and in addition the prior procedure greatly increases the chances of damage to said clockwork by either accidental dropping or striking of the mechanism. Furthermore, the cork wedges, referred to above, have a tendency to work loose, thereby allowing the balance-wheel to rotate.

It is an object of the invention to overcome the disadvantages of the prior art method of locking the balance-wheel of a chronometer or the like.

Another object of this invention is to provide a means for locking the balance-wheel of a chronometer or the like, that will not allow foreign matter to enter the mechanism of the chronometer.

Still another object of this invention is to provide means whereby the balance-wheel of a chronometer or the like may be locked without removing said chronometer from its case.

In accordance with this invention a conventional Hamilton chronometer, or other clock, is modified to the extent of providing, within the interior of the chronometer case, a cantilever-mounted leaf-spring-like member having a pair of rubber buttons or the like mounted at the outer extremity thereof and juxtaposed with the rim of the balance-wheel. The rubber buttons, by virtue of the resiliency of the leaf-spring, normally tend to contact the rim of the balance-wheel of the chronometer, thereby locking the same against movement. A means operable from outside the chronometer case, is provided for lifting the rubber buttons out of contact with the balance-wheel thereby freeing the same for normal movement, said latter means also being adapted to force the buttons into tight contact with the rim of the balance-wheel.

Additional objects and many of the attendant advantages of this invention will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein:

Fig. l is a plan view of the rear of a chronometer, with the case removed, as modified in accordance with this invention;

Fig. 2 is a sectional view on line 2-2 of Fig. l; and

Fig. 3 is a sectional view taken on line 33 of Fig. 2.

Referring now to the drawings, wherein like reference characters designate like or corresponding parts throughout the several views, there is shown in Fig. 1 a plan view of a chronometer 6 provided with a conventional barrel bridge 8 and balance-wheel 10, the chronometer case being removed in this view.

in accordance with this invention a support member 12 is fastened to the barrel bridge 8 by means of screws 14 or the like. The support 12 is provided with an axially extending bore 16, a portion thereof 18 at one end of the support being of reduced diameter and provided with screw threads on the surface thereof.

The chronometer is of course provided with a case 9, a portion of which is shown in Figs. 2 and 3. In order to prevent entry of dust and the like into the interior of the case 9, between said case and the support 12, a plurality of packing rings 11, of Vinylite or the like, are placed around a reduced section of the support 12, between said support and an adjacent opening in the case 9, as shown in Fig. 2.

The portion of support member 12 that is adjacent the barrel bridge 8 is provided with a pair of slots 20 and 22 that are at right angles to each other and intersect at the center of said support. The longitudinal axis of the slot 20 extends at substantially right angles to the axis of rotation of the balance-wheel 10.

The support member 12 is fastened to the barrel bridge 8 astride an elongated, flat, resilient strip 24 made of metal or plastic, said strip 24 having one end fastened to the barrel bridge 8 by a screw 25. The strip extends through the slot 20 in the support member 12, and towards the axis of the balance-wheel 10. The end of strip 24 nearest the balance-wheel is provided with a partially broken away, taken pair of forwardly extending, divergent fingers 26, the I extremity of each of said fingers extending over the rim of the balance-wheel It). A button 28, made of Teflon, rubber or the like, is afiixed to the under side of each arm 26 at the end thereof, both of said buttons being adapted to contact the upper edge of the rim of the balance-wheel 10.

The support member 12 is provided with means operable from outside the chronometer case for lifting the strip 24, thereby raising the buttons 28 out of balancewheel locking position. This means includes an externally threaded screw member 30 having a socket 32 in the upper end thereof, said screw member 30 being screwed into the threaded opening 18 in support member 12, and adapted to move either up or down relative to support 12, depending of course on its direction of rotation. At its lower end the screw 30 is provided with an extension 34 of reduced diameter, said extension having a disc 36 aflixed to the lower end thereof. The disc 36 is rotatably mounted in a slot 40 provided in one end of a piston-like member 38. The upper end of the piston 38 is provided with a cut-away portion, whereby the extension 34 and disc 36 may be moved out of connection with member 38. The piston-like member 38 in turn has an inverted U-shaped member 42 afiixed to the lower end thereof, the bight 43 of said U-shaped member extending transversely of the resilient strip 24.

A straight pin 44 extends between downwardly extending legs 45 of the U-shaped member 42 and has its opposite ends fixed to the respective legs 45. The upper edge of pin 44 is parallel to the adjacent under-surface of the bight 43, and is spaced therefrom a distance substantially equal to the thickness of strip 24.

The strip 24 extends between the legs 45, through the space between pin 44 and bight '43, the space between legs 45 being only slightly greater than the width of strip 24.

To operate the balance-wheel locking means, from an unlocked position, a suitable tool is inserted into socket 32 in the screw member 30 and the latter is rotated in a clockwise direction such that it will move into the support 12. In moving inwardly, the screw 30 causes the piston-like member 38 and the U-shaped member 42 to move toward the barrel bridge 8, by virtue of the rotatable connection of the disc 36, fixedly attached to said screw, with the piston-like member 38 in the slot 40 provided in'said member 38. As the U-shaped member moves toward the barrel bridge, first the resiliency of strip 24 causes it to move the buttons 28 into contact with the balance-wheel rim, and further inward movement of the bight 43 of U-shaped member 42 forces the strip 24 toward the barrel bridge 8, thereby pressing the buttons 28 more firmly against the balance-wheel. It is pointed out that a portion of the U-shaped member 42 is located within the slot 22 in support 12; this, in addition to the size relationship between strip 24 and said U-shaped member 42, prevents rotation of said U-shaped member when screw 30 is rotated. To unlock the balance-wheel 10, it is merely necessary to reverse the direction of rotation of the screw 30, thereby causing the U-shaped member 42 to move away from the barrel bridge 8. When the U-shaped member 42 moves away from the barrel bridge, the pin 44 lifts the strip 24 and thus moves the buttons 28 out of contact with the balance-wheel 10, thereby unlocking the same.

By virtue of the structure described above, the applicant has provided a simple, inexpensive means for locking and unlocking the balance-wheel of a chronometer or the like, without necessitating removal of the chronometer from its case.

Obviously many modifications and variations of the present invention are possible in the light of the above teachings. It is therefore to be understood that within the scope of the appended claims the invention may be practiced otherwise than as specifically described.

What is claimed is:

1. A balance-wheel brake system for a timepiece having a case, a barrel bridge and a balance-wheel having a rim portion, said brake comprising an elongated flexible member having one end attached to said barrel bridge and the remainder thereof adapted to be selectively moved toward said balance-wheel, said flexible member having a pair of divergent arms at one end thereof, a friction member on each of said arms located in a position overlying a side edge of the rim of the balance wheel at diametrically opposite points on said rim; a brake actuating means comprising, a support member with a substantially U-shaped cross-section and having a tubular passageway formed in the bight portion thereof, a portion of said tubular passageway being threaded, a screw member threadedly mounted within the threaded portion of said tubular passageway in the support member, said screw member being selectively movable toward said barrel bridge upon rotation thereof in the proper direction, a piston slidably mounted within the tubular passageway in the support member, said piston having one of its ends rotatably connected to the innermost end of said screw member and having at its opposite end a fixedly connected inverted U-shaped member, a pin extending between and fixedly connected to the leg portions of the U-shaped member and spaced from the bight portion thereof, said elongated flexible member extending between said pin and the bight portion of the U-shaped member, whereby rotation of the screw member causes translation of said piston member and the U-shaped member attached thereto, thereby causing movement of said elongated flexible member relative to the balance-wheel whereby the respective friction members on the divergent arms at the end of the flexible member are adapted to be selectively moved in and out of balance-wheel arresting contact with the edge of the rim of the balance-wheel.

2. A balance-wheel brake system for a timepiece having a case, a barrel bridge and a balance-wheel having a rim portion, said brake comprising an elongated flexile member having one end attached to said barrel bridge and the remainder thereof adapted to be selectively moved toward said balance-wheel, said flexible member having at least one friction member on said flexible mem her and located in a position juxtaposed to, and selectively engageable with, the rim of the balance-wheel; a brake actuating means comprising, a support member with a substantially U-shaped cross section and having a tubular passageway formed in the bight portion thereof, at least a portion of said tubular passageway being threaded, a screw member threadedly mounted within the threaded portion of said tubular passageway in the support member, said screw member being selectively movable toward said barrel bridge upon rotation of the screw in the proper direction, a piston slidably mounted within the tubular passageway in the support member and restricted against rotation relative to said support member, said piston having one of its ends rotatably connected to the innermost end of said screw member, whereby rotation of said screw member causes translation of said piston relative to said support member, means on said piston member in driving engagement with said elongated flexible member, whereby rotation of the screw member causes translation of said piston member and the means thereon connecting said piston member to the flexible member, thereby causing movement of said elongated flexible member relative to the balance-wheel whereby the friction member on the flexible member is adapted to be selectively moved in and out of movement arresting contact with the rim of the balance-wheel.

3. A balance wheel brake system as defined in claim 2, wherein said elongated flexible member has a pair of divergentarms at one end thereof, at least'a portion of each arm being juxtaposed to a side edge of the rim of said balance-wheel, said portion of each arm having one of said friction members attached thereto.

References Cited in the file of this patent UNITED STATES PATENTS 128,283 Cayce June 25, 1872 383,059 Kuhn May 15, 1888 730,208 Geary June 2, 1903 1,755,171 Bartenbach Apr. 22, 1930 1,780,194 Kende Nov. 4, 1930 2,211,077 Schlums Aug. 13, 1940 FOREIGN PATENTS 268,588 Switzerland Sept. 1, 1950 

